The present invention relates to arsenic sulfide compounds. The present invention also relates to pharmaceutical compositions useful for treating cancer, preferably hematological cancer and more preferably leukemia or lymphoma, which comprise an arsenic sulfide compound. The present invention further relates to methods for treating cancer, preferably hematological cancer and more preferably leukemia or lymphoma, using an arsenic sulfide compound. Finally, the present invention relates to processes for producing arsenic disulfide (As4S4).
Cancer
Cancer is characterized primarily by an increase in the number of abnormal cells derived from a given normal tissue, invasion of adjacent tissues by these abnormal cells, and lymphatic or blood-borne spread of malignant cells to regional lymph nodes and to distant sites (metastasis). Clinical data and molecular biologic studies indicate that cancer is a multistep process that begins with minor preneoplastic changes, which may under certain conditions progress to neoplasia.
Leukemia refers to malignant neoplasms of the blood-forming tissues. Transformation to malignancy typically occurs in a single cell through two or more steps with subsequent proliferation and clonal expansion. In some leukemias, specific chromosomal translocations have been identified with consistent leukemic cell morphology and special clinical features (e.g., translocations of 9 and 22 in chronic myelocytic leukemia, and of 15 and 17 in acute promyelocytic leukemia). Acute leukemias are predominantly undifferentiated cell populations and chronic leukemias more mature cell forms.
Acute leukemias are divided into lymphoblastic (ALL) and non-lymphoblastic (ANLL or AML) types. They may be further subdivided by their morphologic and cytochemical appearance according to the French-American-British (FAB) classification or according to their type and degree of differentiation. The use of specific B- and T-cell and myeloid-antigen monoclonal antibodies are most helpful for classification. ALL is predominantly a childhood disease which is established by laboratory findings and bone marrow examination. ANLL or AML occurs at all ages and is the more common acute leukemia among adults; it is the form usually associated with irradiation as a causative agent.
One type of acute leukemias, acute promyelocytic leukemia (APL) is associated with the t(15;17) translocation, which generates a PML/RARxcex1 fusion protein between PML, a growth suppressor localized on nuclear matrix-associated bodies, and RARxcex1, a nuclear receptor for retinoic acid (RA). PML/RARxcex1 was proposed to block myeloid differentiation through inhibition of nuclear receptor response, as does a dominant negative RARxcex1 mutant. In addition, in APL cells, PML/RARxcex1 displaces PML and other nuclear body (NB) antigens onto nuclear microspeckles, likely resulting in the loss of PML and/or NB functions. Diagnosis of acute promyelocytic leukemia (APL) is indicated most importantly on the morphological feature of APL cells in blood and bone marrow. A chromosomal translocation, t(15;17) is also typical of APL and is shown by banding or fluorescence in situ hybridization (FISH) staining techniques. The translocation can often be discovered in patients with APL, especially prior to complete remission. Polymerase chain reaction (PCR) of the patient""s marrow also shows PML/RARxcex1 mRNA. Additionally, certain immunological markers, such as CD33+, CD13+, CD9+ CD34xe2x88x92 and HLA-DRxe2x88x92, are predominantly present in marrow cells.
Chronic leukemias are described as being lymphocytic (CLL) or myelocytic (CML). CLL is characterized by the appearance of mature lymphocytes in blood, bone marrow, and lymphoid organs. The hallmark of CLL is sustained, absolute lymphocytosis ( greater than 5,000/xcexcL) and an increase of lymphocytes in the bone marrow. Most CLL patients also have clonal expansion of lymphocytes with B-cell characteristics. CLL is a disease of older persons. In CML (chronic myelocytic leukemia or chronic myeloid leukemia), the characteristic feature is the predominance of granulocytic cells of all stages of differentiation in blood, bone marrow, liver, spleen, and other organs. In the symptomatic patient at diagnosis the total WBC count is usually about 200,000/xcexcL, but may reach 1,000,000/xcexcL. CML is relatively easy to diagnose because of the presence of the Philadelphia chromosome.
With an incidence of 59,000 cases a year, the malignant lymphomas collectively represent the sixth most common causes of cancer in the United States. They are a heterogeneous group of disorders; about 15% of patients with malignant lymphomas have Hodgkin""s disease, and the remainder have one of the non-Hodgkin""s lymphomas. The etiology, epidemiology, pathology, clinical features, diagnostic evaluation and staging, treatment and management of lymphomas are disclosed in Malignant Lymphomas, the content of which is incorporated herein by reference. CML has been classified according to clinical courses such as, high grade, intermediate grade or low grade CML. Alternatively, CML has been classified according to immunological phenotyping such as T-cell, B-cell, or cytogenetic (chromosomal) aberrations. Histo-pathological changes and morphological changes are very important in the classification of CML. According to the current classification system, the non-Hodgkin""s lymphomas are further subdivided into follicular, small cleaved cell and follicular, mixed small cleaved and large cell lymphoma, small lymphocytic lymphoma, mantle cell lymphoma, mucosa-associated lymphoid tissue lymphoma, monocytoid B cell lymphomas, follicular, large cell lymphoma, diffuse, small cleaved cell lymphoma, diffuse, mixed small cleaved and large cell lymphoma, diffuse, large cell lymphoma, immunoblastic lymphoma, thymic B cell lymphoma, diffuse, small noncleaved cell lymphoma, lymphoblastic lymphoma, peripheral T cell lymphoma, large cell anaplastic lymphoma and non-Hodgkin""s lymphomas in acquired immunodeficiency syndrome.
The very nature of hematopoietic cancer necessitates using systemic chemotherapy as the primary treatment modality. Drugs selected according to sensitivities of specific leukemias and lymphomas are usually given in combination. Radiation therapy may be used as an adjunct to treat local accumulations of leukemic cells. Surgery is rarely indicated as a primary treatment modality, but may be used in managing some complications. Bone marrow transplantation from an HLA-matched sibling is sometimes indicated.
Arsenic and Its Medical Uses
Arsenic has been considered to be both a poison and a drug for a long time in both Western and Chinese medical practices. In the latter part of the nineteenth century, arsenic was used frequently in attempts to treat diseases of the blood in the West. In 1878, it was reported that treatment of a leukemic patient with Fowler""s solution (a solution containing potassium arsenite, valence +5) reduced markedly the count of white blood cells (Cutler and Bradford, Am. J. Med. Sci., January 1878, 81-84). Further interests in the use of Fowler""s solution as a palliative agent to treat chronic myelogenous leukemia (CML) was described by Forkner and Scott in 1931 (J. Am. Med. Assoc., 1931, iii, 97), and later confirmed by Stephens and Lawrence in 1936 (Ann. Intern. Med. 9, 1488-1502). However, while the active chemical ingredient(s) of Fowler""s solution was not determined, its toxicity was well recognized. Fowler""s solution was administered strictly as an oral composition, and was given to leukemic patients as a solution until the level of white blood cells was depressed to an acceptable level or until toxicities (such as skin keratoses and hyperpigmentation) developed, while the patients enjoyed varying periods of remission. In the 1960""s, Fowler""s solution was still used occasionally in attempts to treat CML, however, most patients with CML were treated with other chemotherapeutic agents, such as busulfan, and/or radiation therapy (Monfardini et al., Cancer, 1973, 31:492-501). JP 51-88,620 discloses a process which involves crushing and oxidizing Fe, As and FeS, stirring in water, allowing to stand, and collecting the resulting supernatant containing ferrous, arsenic and sulphate ions, followed by filtration. JP 51-88,620 also discloses that the product of the above process can cure cancerous disease of stomach, duodenum, uterus, lung, pancreas etc.; and is effective in treating diabetes mellitus, heart disease, hypertension, asthma, neuralgia, rheumatism, etc.
Paradoxically, one of the long recognized effects of exposure to arsenic, whether the source is environmental or medicinal, is skin cancer (Hutchinson, 1888, Trans. Path. Soc. Lond., 39:352; Neubauer, 1947, Br. J. Cancer, 1:192). There were even epidemiological data to suggest that the use of Fowler""s solution over long periods could lead to an increased incidence of cancer at internal sites (Cuzick et al., Br. J. Cancer, 1982, 45:904-911; Kaspar et al., J. Am. Med. Assoc., 1984, 252:3407-3408). The carcinogenicity of arsenic has since been demonstrated by the fact that it can induce chromosomal aberration, gene amplification, sister chromatid exchanges and cellular transformation (See e.g., Lee et al., 1988, Science, 241:79-81; and Germolec et al., Toxicol, Applied Pharmacol., 1996, 141:308-318). In a mass screening for cancer in the realgar and tin mines, certain epidemical characteristics were found in precancerous lesion of lung cancer (Wang, Chung Hua Chung Liu Tsa Chih, 1989, 11(3):207-210). Pershagen and Bjorklund, Cancer Lett., 1985, 27(1):99-104, showed that calcium arsenate is tumorigenic, while evidence is inconclusive for arsenic trisulfide (See also Yamamoto et al., Int. J. Cancer, 1987, 40(2):220-223). EPA/600/8-91/061 (OHEA-C-073-005) reports that arsenic and inorganic arsenic compounds, including, inter alia, arsenic disulfide and arsenic trisulfide, are human carcinogens. It further discloses that xe2x80x9csince arsenic compounds are chemically convertible to the carcinogenic form(s) both in vitro and in vivo, and the exact species of inorganic arsenic that is directly carcinogenic in humans is not known, all the above inorganic arsenic compounds are of equal concern.xe2x80x9d Because of the known carcinogenic effect of arsenic, its only therapeutic use in human in Western medicine today is in the treatment of tropical diseases, such as African trypanosomiasis, (the organic arsenical, melarsoprol; See Goodman and Gilman""s The Pharmacological Basis of Therapeutics, 9th edition, chapter 66, 1659-1662, 1997).
In traditional chinese medicine, arsenous acid or arsenic trioxide paste has been used to treat tooth marrow diseases, psoriasis, syphilis and rheumatosis (Chen et al., 1995, in Manual of Clinical Drugs, Shanghai, China, Shanghai Institute of Science and Technology, p.830). In 1970""s, arsenic trioxide had been applied experimentally to treat acute promyelocytic leukemia (APL) in China (commented by Mervis, 1996, Science, 273:578). The clinical efficacy of arsenic trioxide has recently been re-investigated in 14 of 15 patients with refractory APL, where the use of an intravenous dose at 10 mg/day for 4-9 weeks was reported to result in complete morphologic remission without associated bone marrow suppression (Shen et al., 1997, Blood, 89:3354-3360). It was also shown that arsenic trioxide induced apoptosis (programmed cell death) in vitro in NB4 cells, an APL cell line, and that apoptosis was apparently associated with down-regulation of the oncogene bcl-2, and intracellular redistribution of the chimeric PML/RARxcex1 protein that are unique to APL cells (Chen et al., 1996, Blood, 88:1052-1061; Andre et al., 1996, Exp. Cell Res. 229:253-260). It has been reported that the biological activity of arsenic is due to the ability of arsenic to direct the nucleoplasmic fraction of PML to nuclear bodies for degradation (Zhu et al., 1997, Proc. Natl. Acad. Sci., 94:3978-3983).
Realgar (Xiong-Huang), an ore crystal containing mainly arsenic disulfide, has been popular in China for hundreds of years as a drug in traditional medicine and for keeping out the malign among laymen. CN 1,133,725 discloses that an exterior-use plaster which is prepared from 26 Chinese medicinal materials, including inter alia, realgar, can be used in treating liver cancer. CN 1,131,037 discloses that a new anti-carcinogen, suitable for curing exposure carcinosis, can be prepared from 21 Chinese medicinal materials, including inter alia, realgar. CN 1,122,700 discloses that a medicinal powder, comprising garcinia, realgar, frankincense, myrrh, artemisia, rupestris, rosin, vomiting nut and alum, can be used to treat mastosis, mammary tuberculosis sore and tumor. CN 1,119,113 discloses that a compound capsule comprising 24 Chinese medicinal materials, including inter alia, realgar, can be used in preventing and treating various cancers. CN 1,081,104 discloses that a plaster, which is produced from a variety of Chinese medicinal materials, including inter alia, red orpiment (a material similar to realgar), has long-term analgesic effect, especially for soothing cancer pain. CN 1,061,908 discloses that a composition produced from white arsenic, alum, realgar and myrrh can be used to treat cancer.
Although realgar has been used as one component to form a composition that has been indicted useful in treating or preventing various forms of cancer, realgar alone has never been suggested or used to treat cancer, especially leukemias or lymphomas. In addition, arsenic sulfide compound, whether alone or in combination, has never been suggested or used to treat any forms of cancer, including leukemias or lymphomas. On the contrary, there is concern in the medical field that realgar, or certain arsenic sulfide compounds, such as arsenic disulfide and arsenic trisulfide, are human carcinogens.
Qi and Bi, Chung Yao Tung Pao, 1983, 8(5):21 discloses a method of removing AS2O3 from realgar ore using 1% HCl solution. Yuan et al., Chung Yao Tung Pao, 1988, 13(8): 17-21 discloses that treating realgar ore with HCl or vinegar can reduce AS2O3 content in the realgar ore. Yuan et al., Chung Yao Tung Pao, 1988, 13(8):17-21 also discloses that besides As4S4 and AS2O3, realgar contains more than 10 other trace elements, and since the efficacy of realgar depends on all those trace elements, it is a concern that washing realgar with HCl will remove most of the trace elements. Zhang et al., Zhongguo Zhongyao Zaahi, 1995, 20(9):537 discloses that treating realgar ore with yogurt (acidic milk) can reduce realgar""s toxicity.
There is a great need for effective treatments of cancer, particularly hematological cancer including leukemias and lymphomas. Further, there is a great need for orally active anticancer agents. The present invention addresses these and other needs in the art.
Despite reports concerning the risks associated with the administration of arsenic sulfide compound to patients, applicant has discovered surprisingly that certain arsenic sulfide compounds have broad applicability in the treatment of various types of cancers, particularly, hematological cancer including leukemias and lymphomas. The arsenic sulfide compound can be used safely and effectively in mammals. Accordingly, the invention encompasses arsenic sulfide compounds, the preparation of these compounds, their incorporation into pharmaceutical compositions and their use to treat cancer.
The invention described herein encompasses any arsenic sulfide compound, or derivatives thereof, or a mixture with other arsenious compound, that can alleviate, reduce, ameliorate, or prevent cancer; or place or maintain in a state of remission of clinical symptoms or diagnostic markers associated with cancer, particularly hematological cancer including leukemias or lymphomas.
The present invention also encompasses pharmaceutical compositions useful for treating cancer, particularly hematological cancer including leukemia or lymphoma, which comprises an arsenic sulfide compound or realgar, preferably with a pharmaceutically acceptable carrier or excipient. In a preferred embodiment the invention encompasses a composition suitable for oral delivery, comprising one or more arsenic sulfide compounds and a pharmaceutically acceptable carrier or excipient in tablet, capsule, or other single unit dosage form. In another embodiment, the invention includes compositions suitable for topical, transdermal or parenteral delivery. Specific therapeutic regimens, pharmaceutical compositions, and kits are also provided by the invention.
The invention further encompasses a method of treating cancer, particularly hematoligical cancer including leukemia or lymphoma, comprising the administration of a therapeutically effective and non-lethal amount of an arsenic sulfide compound or realgar, preferably with a pharmaceutically acceptable carrier or excipient, to a human in need of such therapy.
The invention also encompasses the use of combination therapy to treat cancers, especially cancers which are refractory to other forms of treatment. In accordance with the present invention, arsenic sulfide compound can be used alone or in combination with other known therapeutic agents (including chemotherapeutics, radioprotectants and radiotherapeutics) or techniques to either improve the quality of life of the patient, or to treat cancer, particularly hematological cancer such as leukemia or lymphoma. The arsenic sulfide compounds can be used before, during or after the administration of one or more known chemotherapeutic agents. In addition, the arsenic sulfide compounds can be used before, during or after radiation treatment. The most preferred combinational therapy is an arsenic sulfide compound and arsenic trioxide used simultaneously or sequentially.
Finally, the invention encompasses a process for producing arsenic disulfide (As4S4) that is substantially free of arsenic trioxide (AS2O3).
Particular compositions of the invention and their uses are described in the sections and subsections which follow.